Menstruation: Postponing Periods by Dr Azmy Birdi

The holiday hormone: Norethisterone

As the Easter break approaches, so do the requests for that holiday essential: Norethisterone.

However, there is good reason for exercising caution before getting a prescription for hormonal medication to postpone or delay a period.(J Fam Plann Reprod Health Care 2012;38:148).

What is Norethisterone? 

It is a hormone (type of Progestogen) derived from testosterone.

It is used in the combined hormonal contraceptive pill  and hormone replacement preparations. 

 It is prescribed as a treatment for dysfunctional (irregular) vaginal  bleeding, as part of hormone replacement therapy (HRT)  and postponement of menstruation. 

To postpone periods: the dose is 5 mg to be taken 3 times a day, starting 3days before expected onset of the period, until no longer needed.

Risk of Venous Thromboembolism or Deep Vein Thrombosis  (DVT) 

Studies have reported increased risk of DVT in women taking progestogens such as norethisterone in high doses.

Further research has found that norethisterone is partially metabolised to ethinyloestradiol (estrogen)

This conversion is not important at low doses (e.g. in Combined pill or HRT), but a daily dose of 10–20mg of norethisterone is estimated to be equivalent to taking a 20–30mcg pill. This may explain its efficacy in controlling menstruation.

MHRA (Medicines & Healthcare products  Regulatory Agency) guidance

Norethisterone should not be prescribed in the following situations:

-Pregnancy

-Hepatic disease

-History of breast cancer

-Undiagnosed vaginal bleeding

-Genital tract tumours

-High risk of arterial disease

-History of a DVT 

The SPC (summary of Product Characteristics) for Primulut (a brand of Norethisterone) lists migraine with aura as a contraindication, and includes a section warning about the conversion  to ethinyloestradiol.

In summary:

Therapeutic norethisterone should be regarded as a combination-like product with oestrogenic properties and inherent  risk of venous thromboembolism , so apply the same risk assessment categories as with combined hormonal preparations, i.e. treat it like the pill.

Alternative treatments for delaying periods 

One small study has suggested 10mg medroxyprogesterone acetate taken 3 times a day is as effective as norethisterone, without the associated risks.

Remember: neither norethisterone nor medroxyprogesterone acetate are licensed for contraception in these doses.